Indeed, high mutation rates are seen in Northern and Eastern European countries (Vahteristo et al. 2002; CHEK2 Breast Cancer Case–control Consortium CHEK2*1100delC and susceptibility to breast cancer 2004; Meijers-Heijboer et al. 2002) although its frequency is much lower in North America (Mateus Pereira et al. 2004; Offit et al. 2003), whereas the mutation does not seem to be a triggering factor to breast cancer in Poland (Kwiatkowska et al. 2006; Cybulski et al. 2004) and some multiple-case breast cancer families from Australia (Jekimovs et al. 2005). This evidence concerns the gene CHEK2 and breast cancer.